1. Technical Field of the Invention
The present invention relates to a motor driving apparatus constituted of a driver IC which integrally comprises a driving circuit for driving a plurality of loads (coils etc.) contained in a plurality of motors built in, for example, a camera and a control circuit for controlling the driving circuit to thus drive the plurality of motors sequentially.
2. Prior Art
For example, a digital camera equipped with a plurality of motors as sources for driving a variety of working parts. These may include a stepping motor, an iris motor, and a DC motor. In particular, as for a lens-barrel, a stepping motor is used to drive a lens for, for example, auto focusing. An iris motor is used to drive a shutter and a diaphragm. In some cases, the iris motor is replaced by the stepping motor to drive a diaphragm. The DC motor is used to drive a zoom lens. In some cases, the DC motor is replaced by the stepping motor to drive the zoom lens.
The stepping motor is comprised of, for example, a multi-pole magnetized rotor, a stator, and a 2-phase coil in which two coils work as two loads. Therefore, to drive a stepping motor, the driver IC is provided with a total of four output terminals in two pairs capable of driving the two loads. Typically, each pair of the output terminals corresponds to one H-type bridge circuit, so that the driver IC comprises two H-type bridge circuits for driving one stepping motor. The iris motor is constituted of a 2-pole magnetized rotor and one coil. Therefore, to drive the iris motor, the driver IC needs to be provided with only one pair of output terminals. Furthermore, to drive the DC motor, at least one pair of output terminals is required.
In a lens-barrel for camera, as zoom-lens driving motors (zoom motors), a DC motor and a stepping motor are used typically. Occasionally, there occurs such a compensation request as auto focusing (AF) or diaphragm adjustment as interlocked with zooming, so that the zoom motor is desired to be driven as coordinated with the other motors. If, in this case, the DC motor is used for zooming, the DC motor needs to be driven simultaneously with the other motors. Therefore, the DC motor needs to be provided with a separate driving circuit independent of the other motors, thereby increasing the number of parts to be mounted, and giving rise to a problem to be solved. If the stepping motor is used for zooming, on the other hand, it can be driven sequentially with the other motors and so need not necessarily be driven simultaneously. Therefore, the stepping motor used for zooming and the other stepping motors can be driven sequentially by the common driver IC. However, if a driving circuit is provided independently for the DC motor for zooming, it cannot drive the zooming stepping motor, thereby giving rise to a problem of a poor versatility as a driver circuit IC.
In view of the above problems of the conventional technologies, it is an object of the invention to provide a motor driving apparatus that can be applied to, for example, both a DC motor and a stepping motor, using one driving circuit. It is another object of the invention to provide a motor driving apparatus having a circuit configuration that can accommodate a large variety of combinations of motors flexibly. To achieve these objects, the following means have been provided. That is, a motor driving apparatus according to one aspect of the invention comprises a driving circuit for driving a plurality of loads contained in a plurality of motors, and a control circuit for controlling the driving circuit to sequentially drive the plurality of the motors, wherein the driving circuit has at least two channels which are controlled by the control circuit concurrently with each other, each channel is controlled by the control circuit such as to selectively drive the loads, the channel is provided with at least (n+1) number (n: integer of 2 or greater) of output terminals to connect at most n number of the loads, and the control circuit controls the driving circuit to perform an intra-channel driving mode in which one pair of the output terminals are selected from one channel and allocated to drive one load, and an inter-channel driving mode in which another pair of the output terminals are selected from two channels and allocated to drive another load. The motor driving apparatus having such a configuration can be applied to controlling of a plurality of motors integrated in a lens-barrel provided with a plurality of mechanisms used in photographing by camera which are selected from a shutter mechanism, a diaphragm mechanism, an auto focusing mechanism, and a zooming mechanism.
Preferably, the driving circuit has a first channel and a second channel, and wherein an output terminal is separated from the first channel, another output terminal is separated from the second channel and the separated output channels are paired to constitute a third channel capable of driving a load under the inter-channel driving mode. For example, the driving circuit has seven input terminals connected to the control circuit, the first channel having three output terminals, the second channel having three output terminals, and the third channel having two output terminals separated from the first channel and the second channel, and the control circuit can control the driving circuit to drive a load through the third channel concurrently with driving of other loads through the first and second channels. Typically, the third channel is allocated to drive a DC motor composed of one load. In a practical form, the driving circuit is connected to drive a stepping motor simultaneously with another motor, the stepping motor being composed of two loads allocated to two channels respectively, and the control circuit can select either of the intra-channel driving mode or the inter-channel driving mode for driving said another motor. Expediently, the driving circuit can drive the stepping motor simultaneously with a DC motor as said another motor, and performs 2-phase driving of the two loads of the stepping motor through the two channels. Otherwise, the driving circuit can drive the stepping motor simultaneously with a DC motor as said another motor, and performs 1-2-phase driving of the two loads of the stepping motor through the two channels.
A motor driving apparatus according to another aspect of the invention comprises a driving circuit for driving a plurality of loads contained in a plurality of motors, and a control circuit for controlling the driving circuit to sequentially drive the plurality of the motors, wherein the driving circuit has at least two channels which are controlled by the control circuit concurrently with each other, each channel is controlled by the control circuit so as to selectively drive the loads, the channel is provided with at least (n+1) number (n: integer of 2 or greater) of output terminals to connect at most n number of loads such that two output terminals are allocated to drive one load, and the control circuit controls the driving circuit to perform either of an intra-channel driving mode in which a pair of the output terminals are selected from one channel and allocated to drive a load, and an inter-channel driving mode in which a pair of the output terminals are selected from two channels and allocated to drive a load. When the driving circuit is connected to drive a stepping motor composed of two loads sequentially with another motor, the control circuit can select either of the intra-channel driving mode and the inter-channel driving mode for driving said another motor. When the driving circuit is connected to drive a DC motor as said another motor, an output terminal is separated from one channel, another output terminal is separated from another channel and the separated output channels are paired to constitute an additional channel capable of driving the DC motor concurrently with the stepping motor under the inter-channel driving mode. The motor driving apparatus having such a configuration can be applied to controlling of a plurality of motors integrated in a lens-barrel of a camera provided with a plurality of mechanisms used in photographing which are selected from a shutter mechanism, a diaphragm mechanism, an auto focusing mechanism, and a zooming mechanism.
According to the invention, the motor driving apparatus (driver IC) is capable of selecting intra-channel driving mode as well as inter-channel driving mode of loads. By intra-channel driving mode, one pair of output terminals are allocated in one channel to drive one load. By inter-channel driving mode, one pair of output terminals are allocated over two channels to drive one load. For example, to drive a DC motor comprised of one load, inter-channel driving mode is performed. In this case, the respective output terminal allocated to the DC motor in each channel is separated from bridge connection with the remaining output terminals. Therefore, the DC motor can be driven simultaneously with the other motors such as a stepping motor.